Database performance can be enhanced by distributing information, such as source tables, among multiple hosts. For example, a number of hosts may store different tables in the database system, or tables can be partitioned among multiple hosts. The ability to distribute a database system among multiple hosts can provide opportunities to increase system performance, such as by distributing workloads among CPUs located at the different hosts, rather than relying on the capabilities of a single host. However, distributed systems can present challenges in ensuring that database operations are carried out in a way that provides queries with accurate data, but without requiring so much coordination between hosts that the performance of the distributed system is significantly adversely affected.